1. Field of the Invention
The present invention relates to a numerical controller for controlling a five-axis machining apparatus having three linear axes and two rotary axes, and more particular, to a numerical controller for performing control to realize highly accurate machining by setting compensation amounts corresponding to errors, such as linear axis-dependent and rotary axis-dependent translational errors which are respectively dependent on linear and rotary axis positions, thereby moving a tool end point position to an accurate position.
2. Description of Related Art
JP3174704B discloses a technique in which a coordinate system is divided into lattice regions, lattice point compensation vectors measured at lattice points are stored, and a current position compensation vector for use in compensation is calculated based on lattice point compensation vectors. This disclosed technique implements only linear axis-dependent translational compensation, and therefore cannot carry out linear axis-dependent rotational compensation, rotary axis-dependent rotational compensation, and rotary axis-dependent translational compensation.
JP2005-59102A discloses a technique for correcting the machining origin based on a rotary axis error with respect to a reference axis. This disclosed technique only implements rotary axis-dependent translational compensation, and cannot carry out linear axis-dependent translational compensation, linear axis-dependent rotational compensation, and rotary axis-dependent rotational compensation.
JP2004-272887A discloses a compensation technique for maintaining a relation between a tool and a workpiece found when there is no mechanical error on the basis of an amount of misalignment of a rotary axis and an amount of misalignment of the turning center of the spindle. This disclosed technique only takes into account the amount of misalignment of the rotary axis and that of the turning center of the spindle, thus entailing a difficulty in realizing accurate compensation. This patent publication does not disclose a technique for storing in advance compensation amounts at division positions in each axis coordinate system and determining a compensation amount for a command position based on stored compensation amounts.
JP2007-168013A discloses a technique for calculating the position of a cutting edge of a tool being used on the basis of a rotary axis position (index angle of inclined feed axis), a tool length (distance from a front end surface of the tool spindle to the cutting edge being used), measured distances from the front end surface to a plurality of reference points on a test bar, and measured positions of the reference points. With this technique, only rotary axis-dependent rotational compensation is performed through three linear axes and two rotary axes for head rotation in a five-axis machining apparatus, and therefore, linear axis-dependent translational compensation, linear axis-dependent rotational compensation, and rotary axis-dependent translational compensation are difficult to carry out.
The five-axis machining apparatus for machining a workpiece through three linear axes and two rotary axes produces four primary errors including translational errors, (1) a linear axis-dependent translational error which is dependent on linear axis position and (2) a rotary axis-dependent translational error which is dependent on rotary axis position, and rotational errors, (3) a linear axis-dependent rotational error which is dependent on linear axis position and (4) a rotary axis-dependent rotational error which is dependent on rotary axis position.